The present invention relates to a pressure control valve for a hydraulic actuator system or the like.
Pressure relief valves are widely used in the art for limiting hydraulic oil pressure to a predetermined maximum value. There are generally two types. A first type comprises a spring loaded relief poppet which is unseated to connect a pressure line to a return line when the pressure in the pressure line exceeds the predetermined value. A second type is similar to the first type but further comprises a pilot poppet to amplify the pressure variation and control the relief poppet with greatly improved accuracy.
However, a problem has remained unsolved in the design of such valves, the closest known prior art being constituted by U.S. Pat. No. 3,164,166, in that the relief poppet opens too much, causing the pressure to undershoot the predetermined value by a large amount before stabilization and disrupt the hydraulic control system which is regulated by the control valve.
An improvement to the basic valve is disclosed in U.S. patent application Ser. No. 121,609, filed Feb. 14, 1980 which is assigned to the same assignee as this application. The improvement is to provide a ratio A.sub.P /A.sub.R .gtoreq.1.1, where A.sub.R is an area of the piston poppet exposed to pressure in the pressure port and A.sub.P is an area of the pilot poppet exposed to pressure in the back pressure chamber. The present invention provides an improved arrangement which yet further improves the pressure control.